The striatal complex constitues a large, cental mass in the forebrain of all mammals. The traditional clinical view that it subserves purely motor functions is not supported by findings that large bilateral lesions of it may result in no motor deficits. Earlier work on this project revealed findings in support of the hypothesis that the striatal complex palys a fundamental role in species-typical, prosematic (non-verbal) behavior involved in social communication. The present studies represent a continuation of that investigation, testing the effects of lesions of the supranigral tegmentum on the somatic and autonomic components of the innate mirror display of gothic-type squirrel monkeys. The findings provide evidence that extensive lesions of the supranigral tegmentum that encompass pathways to and from the striatal complex may eliminate all aspects of the display behavior.